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Note: Before March 1, 1989 and after March 22, 1993, the OSHA PEL is [(10 mg/m3) /(% quartz + 2)] for respirable dust containing at least 1 percent quartz. From March 1, 1989 to March 22, 1993, the OSHA PEL was 0.1 mg/m3 for respirable quartz. See appendices